Thermal relay



Oct. 12 1926. 1,602,952

B. H. SMITH THERMAL RELAY Original Filed June-9. 1920 INVENTOR Hyg Hy 4 Benjgfam /z' Sml #2 2 ATTORNEY WITNESSES: 19

Patented Oct. 12, i926.

UNITED STATES PATENT oFFicr..

BENeTAm H. SEITE; 0l' WILmSBUBG, PENNSYLVANIA. ASSIGNOB T0 WESTING- HOUSE ELECTRIC IANUFACTUBING COMPANY, A CORPORATION 0F PENNSYL- VARIA.

THERMAL RELAY.

Appueqm ma me a, im. semi ne. :suse renewed :une e, um.

My invention relates to relays and particularly to thermal relays of the cartridgeing. f y

A further object of my invention is to provide a relay, of the above indicated character, that shall be simple and inexpensive to construct and effective in its operation.

In racticing my invention, I provide a c lin rical casing, metallic end errules' t erefor and a reinforcing metallic cylindrical member for the casing. The bimetallic member is slit from opposite ends thereof to increase the resistance of the same and to provide two terminals therefor at one end. The terminal end of the bimetallic member is mechanicall connected to one ferrule by bein moul ed thereto, and an adjustable stationary contact member is jmoulded in position with respect to the other ferrule.

One terminal of the bimetallic element is electrically connected tothe lferrule to which it is mechanically connected, and the other terminal is disposed to engage a metallic reinforcing member.

One of the ferrules is insulated from the metallic reinforcing member and the other is electrically connected thereto. With this arrangement, the co-o erating portions of the relay are effective y held in alinement, irrespective of the positions of the fuse clips in which it is disposed, and the reinforcing member serves as a connecting means Whereby the bimetallic member is placed in series with the ferrules without the use of auxiliary conductors.

Figure l of the accompanying drawings comprises a diagrammatic view of an electric circuit and a sectional view of a relay embodying my invention.

Fig. 2 is a side elevational view of the bimetallic member shown in Fig. 1.

Fig. 3 is a plan view of the bimetallic member shown in Fig. 2.

Fig. 4 is a detail plan view, with parts cut away, of the insulating and contact member embodying my invention, and

Fig. 5 is an end view of the contact niembers shown in Fig. 4. v

An electrical translating device 1 is connected, to an electric circuit 2 and is provided with a circuit interru ter 3 for disconnecting the same when t e device 1 attains dangerous temperatures. The interrupter 3 is provided with a holding electromagnet 4 anda spring 5 for actuating the same. `The holding electromagnet 4 is controlled b a thermal relay 6.

The re ay 6 comprises, in general, a cylindrical insulating casing 7, two metallic end ferrules 8 and 9, a metallic reinforcing meinber 10, a stationary contact member 11 and a bimetallic member 12 upon which a contact member 13 is mounted.

The bimetallic member 12 is slit from oppositeends thereof to increase its resistance and thereby to generate suliicient heat, when traversed by a relatively small value of current, to permit the use of a suiciently rigid bimetallic member to obtain effective contact engagement. The bimetallic member 12 is so slit as to have its two terminals 14 and 15 at one' end thereof.

The bimetallic member 12, by reason of its shape and relatively great current-conducting length, develops a relatively -large amount of heat and, b reason of the lagging efl'ect of the cylindrical casing, follows a temperature curve that substantially follows thev temperature characteristic of the apparatus in the circuit that is to be., protected. The temperature curve of the relay may be made either to correspond to the temperature of the device to be protected oru to embody la time element that is sufficient to effect protection of the device to be protected.

A body 16 of insulating material is kmoulded around the Contact end of the bimetallic member 12 to ret-ain the lsame in position in the ferrule 9. The terminal 14 is soldered, or otherwise electrically secured, to the ferrule 9, and the terminal 15 is so disposed as to slide in an opening 17 in the member 10 when the ferrule 9 is placed in position to eect engagement therewith.l

The contact member 13 is connected to the bimetallic member at a portion 19 and is insulated :from the remainder ofthe bimetallic element by an insulating strip 2O for the purpose of precluding short circuiting the various portions thereof.

The stationary contact member 11 is tapered and is provided with nuts 22 to permlt the position of the same to be adJusted wlth respect to the contact member 13. The ferrule 8 is electrically connected tothereinforcing member 10 by screws 23.

The contact member 11 .of the relay 6 1s connected, through the electromagnet 4, to the conductor 24 of the circuit 2, and the ferrules 8 and 9 are connected in series with the conductor 25 of the circuit 2. Since the contact member 13 is electrically connected to the bimetallic element 12 and, since the bimetallic element is connected in series with the conductor 25, it will be understood that the electromagnet 4 is connected across the circuit 2 and thus constitutes a low-voltage trip coil as well as an elctromagnet that is controlled by a device which is responsive to the temperature of the device to be protected.

It will be seen, from the above, that the main circuit of the current through the relay device 6 extends from the 30 ferrule 8 through the screws 23, reinforcing member 10, the terminal 15 of the bimetallic element 12, the various separated portions of the I bimetallic element, and the terminal 14 of the bimetallic element to the ferrule 9. From this, it will be understood that no auxiliary conductors are necessary to connect the bimetallic element in series with the circuit.

The casing 7 so heat lags the element 12 and the resistance of the element 12 is such that suiiicient heat is generated therein to cause the same to either have the same heating characteristic as the device to be protected or to require such time to operate that effective protection of the device 1 ma be obtained. When sutlicient heat has een generated in the bimetalic element 12, the same operates to disengage the contact members 11 and 13 and thus de-energizes the winding of the electromagnet 4 which permits the spring 5 to open the interrupter.

The reinforcing member 10 serves the double purpose of aligning the co-operating members of the rela and also of electrically connecting the con ucting member between the ferrules to preclude the necessity of using auxiliary conductors which are usually a source of trouble indevices of this character.

My invention is not limited to the specific structure illustrated, as it may be variously modified within the spirit and scope of the invention, as set forth in the appended claims.

I claim as my invention:

1. A thermal relay comprising a cylindrical casing having a metallic reinforcing member therein, end ferrules one only of which is electrically connected to the reinforcing member, a current-traversed bimetallic member having longitudinal slits therein mechanically and electrically connected to one ferrule and electrically connected t0 the reinforcing member, and an adjustable contact member mechanically connected to the other ferrule.

2. A thermal relay comprising a cylindrical insulating casing, a cylindrical metallic reinforcing member therefor disposed therein, two connecting ferrules, an adjustable stationary contact member, a current-traversed bimetallic strip, moulded means for mechanically securing one end of the strip to one ferrule and means for electrically securing a ortion of that end of the strip to the ferru e and another portion thereof to the reinforcing member.

3. A thermal relay comprising a cylindrical metallic member, two ferrules for the ends thereof, a bimetalic member having slits therein extending from opposite ends thereof, moulded means for securing one end of the bimetallic member to one ferrule, and means for connecting the bimetallic member in series with the fcrrules through the cylindrical metallic member.

4. A thermal relay comprising a cylindrical casing, two end ferrules, a bimetallic member secured to one ferrule, and beingi` so slit from the 'opposite ends thereof as to have its two terminals at one end thereof, means for securing the terminal end of the bimetallic member to one ferrule, a metallic cylindrical member closely fitted within the casing, and means whereby one terminal of the bimetallic member is electrically connected to the metallic cylindrical member.

5. A thermal relay comprising a metallic cylindrical member, two end ferrules, a bimetallic member so slit as to have its two terminals at one end, means for connecting one terminal to the ferrule upon which the bimetallic member is mounted and means for so connecting the other terminal to the cylindrical member that the bimetallic member is connected in series with the ferrules without the use of auxiliary conductors.

6. A thermal relay comprising a heat-insulated metal casing, thermally-influenced current traversed'means extendlng longitudinally therein, means co-operating with said casing and said thermally-influenced current traversed means for establishing a main electric circuit through the relay, and means co-operating with said thermally-influenced 'current traversed means for normallv establishing a control circuit therethrough.

In testimony whereof, I have hereunto subscribed my name this 4th day of June, 1920.

BENJAMIN H. SMITH. 

